Radio frequency circuit and communication device

ABSTRACT

A radio frequency circuit includes a first acoustic wave filter that is connected to a common terminal and includes a first acoustic wave resonator, a first LC filter that is connected to the common terminal via the first acoustic wave filter and includes at least one of an inductor or a capacitor, a second acoustic wave filter that is connected to the common terminal and includes a second acoustic wave resonator, and a second LC filter that is connected to the common terminal via the second acoustic wave filter and includes at least one of an inductor or a capacitor.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 17/658,899 filed on Apr. 12, 2022, which is a continuation ofU.S. patent application Ser. No. 16/887,169 filed on May 29, 2020, whichclaims priority of Japanese Patent Application No. 2019-101466 filed onMay 30, 2019. The entire disclosure of each of the above-identifiedapplications, including the specification, drawings and claims isincorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to a radio frequency circuit and acommunication device.

BACKGROUND

In recent communication services, communication bandwidth has beenincreased and communication bands have been used simultaneously so as toachieve high-capacity and high-speed communication.

Patent Literature (PTL) 1 (Japanese Unexamined Patent ApplicationPublication No. 2006-128881) discloses a multiplexer that multiplexesand demultiplexes radio frequency signals in two different communicationbands. The multiplexer disclosed in PTL 1 includes aninductive-capacitive (LC) filter including an inductor and a capacitor.Accordingly, such a multiplexer multiplexes and demultiplexes radiofrequency signals in a wide communication band.

BRIEF SUMMARY

For example, in the fifth generation mobile communication system (5G) tobe introduced in the foreseeable future, a communication band has ahigher frequency and a wider bandwidth, whereas a frequency interval(frequency gap) between two different communication bands is relativelynarrow. When a communication band has a wider bandwidth and a frequencygap between two different communication bands is small as above, sinceattenuation slopes at both ends of a passband are not steep, amultiplexer including an LC filter as described in PTL 1 cannot ensureisolation between the two different communication bands. Accordingly,the propagation loss of radio frequency signals in the two differentcommunication bands is increased.

In view of the above, the present disclosure has been conceived to solvethe above problem, and has an object to provide radio frequency circuitsand communication devices that multiplex or demultiplex radio frequencysignals in communication bands with high isolation and low loss.

In order to achieve the above object, a radio frequency circuitaccording to one aspect of the present disclosure includes: a commonterminal; a first acoustic wave filter that is connected to the commonterminal and includes a first acoustic wave resonator; a first LC filterthat is connected to the common terminal via the first acoustic wavefilter and includes at least one of an inductor or a capacitor; a secondacoustic wave filter that is connected to the common terminal andincludes a second acoustic wave resonator; and a second LC filter thatis connected to the common terminal via the second acoustic wave filterand includes at least one of an inductor or a capacitor.

The present disclosure provides radio frequency circuits andcommunication devices that multiplex or demultiplex radio frequencysignals in communication bands with high isolation and low loss.

BRIEF DESCRIPTION OF DRAWINGS

These and other advantages and features will become apparent from thefollowing description thereof taken in conjunction with the accompanyingDrawings, by way of non-limiting examples of embodiments disclosedherein.

FIG. 1 is an example of a circuit configuration diagram illustrating aradio frequency circuit and a communication device according to anembodiment.

FIG. 2A is an example diagram illustrating passing characteristics andcombined passing characteristics of an acoustic wave filter and an LCfilter included in the radio frequency circuit according to theembodiment.

FIG. 2B is an example diagram illustrating passing characteristics ofthe radio frequency circuit according to the embodiment.

FIG. 3A is an example of a circuit configuration diagram illustrating aradio frequency circuit and an antenna element according to Variationembodiment 1 of the embodiment.

FIG. 3B is an example of a circuit configuration diagram illustrating aradio frequency circuit and an antenna element according to Variationembodiment 2 of the embodiment.

FIG. 3C is an example of a circuit configuration diagram illustrating aradio frequency circuit and an antenna element according to Variationembodiment 3 of the embodiment.

FIG. 4A is a diagram illustrating the first example of a circuitconfiguration of an acoustic wave filter according to the embodiment.

FIG. 4BA is a diagram illustrating the second example of a circuitconfiguration and FIG. 4BB is an example graph diagram showing passingcharacteristics of an acoustic wave filter according to the embodiment.

FIG. 4C is a diagram illustrating an example of a circuit configurationof the LC filter according to the embodiment.

FIG. 5 is an example of a circuit configuration diagram illustrating aneighborhood of a connection node between the acoustic wave filter andthe LC filter of the radio frequency circuit according to theembodiment.

FIG. 6A is an example of a circuit configuration diagram in which theradio frequency circuit according to the embodiment is used forcommunication bands of the fourth generation mobile communication system(4G) Long Term Evolution (LTE) and 5G New Radio (NR), and FIGS. 6B, 6C,and 6D illustrate example graphs showing passing characteristics.

FIG. 7 is an example of a circuit configuration diagram illustrating aradio frequency circuit according to Variation embodiment 4 of theembodiment, and peripheral circuitry of the radio frequency circuit.

DETAILED DESCRIPTION

The following describes in detail embodiments of the present disclosurewith reference to the drawings. It should be noted that the embodimentand variations described blow each show a general or specific example.The numerical values, shapes, materials, elements, the arrangement andconnection of the elements, etc. indicated in the embodiment andvariations are mere examples, and therefore are not intended to limitthe present disclosure. Thus, among the elements in the followingembodiment and variations, those not recited in any independent claimare described as optional elements. In addition, the sizes of elementsand the ratios of the sizes illustrated in the drawings are notnecessarily accurate.

1. Embodiment of Configurations of Radio Frequency Circuit andCommunication Device

FIG. 1 is an example of a circuit configuration diagram illustratingradio frequency circuit 1 and communication device 5 according to theembodiment. As illustrated in FIG. 1 , communication device 5 includesradio frequency circuit 1, antenna element 2, radio frequency (RF)signal processing circuit (RFIC) 3, and baseband signal processingcircuit (BBIC) 4.

Radio frequency circuit 1 includes common terminal 100, multiplexer 11,LC filters 12A and 12B, low-noise amplifiers 21A and 21B, and receptionoutput terminals 110A and 110B.

Multiplexer 11 includes acoustic wave filters 11A, 11B, 11C, and 11D. Itshould be noted that acoustic wave filters 11A to 11D have mutuallynon-overlapping passbands.

Acoustic wave filter 11A is an example of a first acoustic wave filter.Specifically, acoustic wave filter 11A is a radio frequency filter thathas an input terminal (a first input/output terminal) and an outputterminal (a second input/output terminal), and includes a first acousticwave resonator. The input terminal of acoustic wave filter 11A isconnected to common terminal 100. The output terminal of acoustic wavefilter 11A is connected to connection node n1. The first acoustic waveresonator is, for example, an acoustic wave resonator that uses surfaceacoustic waves (SAWs) or an acoustic wave resonator that uses bulkacoustic waves (BAWs).

Acoustic wave filter 11B is an example of a second acoustic wave filter.Specifically, acoustic wave filter 11B is a radio frequency filter thathas an input terminal (a third input/output terminal) and an outputterminal (a fourth input/output terminal), and includes a secondacoustic wave resonator. The input terminal of acoustic wave filter 11Bis connected to common terminal 100. The output terminal of acousticwave filter 11B is connected to connection node n2. The second acousticwave resonator is, for example, an acoustic wave resonator that usesSAWs or an acoustic wave resonator that uses BAWs.

Acoustic wave filter 11C is a radio frequency filter that has an inputterminal and an output terminal, and includes an acoustic waveresonator. The input terminal of acoustic wave filter 11C is connectedto common terminal 100. Acoustic wave filter 11D is a radio frequencyfilter that has an input terminal and an output terminal, and includesan acoustic wave resonator. The input terminal of acoustic wave filter11D is connected to common terminal 100. The above acoustic waveresonators are each, for example, an acoustic wave resonator that usesSAWs or an acoustic wave resonator that uses BAWs.

It should be noted that multiplexer 11 may have a configuration thatdemultiplexes radio frequency signals in at least two differentfrequency ranges (communication bands). From this point of view, thenumber of radio frequency filters included in multiplexer 11 may be twoor higher.

LC filter 12A is an example of a first LC filter. Specifically, LCfilter 12A is a radio frequency filter that has an input terminal (afifth input/output terminal) and an output terminal (a sixthinput/output terminal), and includes at least one of an inductor or acapacitor. The input terminal of LC filter 12A is connected to theoutput terminal of acoustic wave filter 11A via connection node n1. Theoutput terminal of LC filter 12A is connected to terminal 160A.

LC filter 12B is an example of a second LC filter. Specifically, LCfilter 12B is a radio frequency filter that has an input terminal (aseventh input/output terminal) and an output terminal (an eighthinput/output terminal), and includes at least one of an inductor or acapacitor. The input terminal of LC filter 12B is connected to theoutput terminal of acoustic wave filter 11B via connection node n2. Theoutput terminal of LC filter 12B is connected to terminal 160B.

It should be noted that although circuit elements connected to theoutput terminals of acoustic wave filters 11C and 11D are omitted inFIG. 1 , LC filters may be connected to these respective outputterminals.

Low-noise amplifier 21A is an example of the first amplifier, and has aninput terminal connected to the output terminal of LC filter 12A viaterminal 160A, and an output terminal connected to reception outputterminal 110A. Low-noise amplifier 21A amplifies a received radiofrequency signal that has been inputted from common terminal 100 and haspassed through acoustic wave filter 11A and LC filter 12A, and outputsthe amplified radio frequency signal to RFIC 3.

Low-noise amplifier 21B is an example of a second amplifier, and has aninput terminal connected to the output terminal of LC filter 12B viaterminal 160B, and an output terminal connected to reception outputterminal 110B. Low-noise amplifier 21B amplifies a received radiofrequency signal that has been inputted from common terminal 100 and haspassed through acoustic wave filter 11B and LC filter 12B, and outputsthe amplified radio frequency signal to RFIC 3.

It should be noted that input terminal sides of low-noise amplifiers 21Aand 21B often have a configuration in which capacitors are connected inseries. Consequently, it is desirable that output terminal sides of LCfilters 12A and 12B have a configuration in which capacitors areconnected in series. Accordingly, it is possible to optimize animpedance matching between low-noise amplifier 21A and LC filter 12A,and an impedance matching between low-noise amplifier 21B and LC filter12B.

It should be noted that although radio frequency circuit 1 according tothe present embodiment is a reception circuit that transfers radiofrequency signals received by antenna element 2 to RFIC 3, radiofrequency circuit 1 may be a transmission circuit that transfers radiofrequency signals outputted from RFIC 3, to antenna element 2. Whenradio frequency circuit 1 is configured as a transmission circuit, poweramplifiers are disposed instead of low-noise amplifiers 21A and 21B.Further, radio frequency circuit 1 may be a transmission and receptioncircuit having both functions of transmissions and receptions.

It should be noted that multiplexer 11 and LC filters 12A and 12B mayconstitute radio frequency module 10 disposed on the same substrate asthese components. For example, LC filters 12A and 12B may each includean inductor having a planar coil pattern in the substrate, and acapacitor having a planar electrode in the substrate, and multiplexer 11may be mounted on the substrate.

Further, radio frequency circuit 1 does not necessarily includelow-noise amplifiers 21A and 21B.

The following describes elements other than radio frequency circuit 1that constitute communication device 5.

Antenna element 2 is connected to common terminal 100 of radio frequencycircuit 1, and receives radio frequency signals. Moreover, when radiofrequency circuit 1 is configured as a transmission circuit or atransmission and reception circuit, antenna element 2 may emit radiofrequency signals transferred to radio frequency circuit 1 from RFIC 3.

RFIC 3 processes radio frequency signals outputted from radio frequencycircuit 1 via reception output terminals 110A and 110B. Moreover, whenradio frequency circuit 1 is configured as a transmission circuit or atransmission and reception circuit, RFIC 3 processes a transmissionsignal inputted from BBIC 4 by up-conversion etc., and outputs radiofrequency signals generated by being processed to radio frequencycircuit 1. Furthermore, RFIC 3 includes a controller that outputs acontrol signal for switching connection states of switch circuits 13 to15 to be described below, based on a communication band to be used. Itshould be noted that the controller may be disposed outside RFIC 3, andmay be disposed in, for example, radio frequency circuit 1 or BBIC 4.

BBIC 4 performs signal processing using an intermediate frequency bandhaving a frequency lower than that of radio frequency signalstransferred through radio frequency circuit 1. A signal processed byBBIC 4 is used as, for example, an image signal for displaying an imageor an audio signal for talking via a loudspeaker.

2. Passing Characteristics of Radio Frequency Circuit 1 According to theEmbodiment

FIG. 2A is an example diagram illustrating passing characteristics andcombined passing characteristics of acoustic wave filter 11A and LCfilter 12A included in radio frequency circuit 1 according to theembodiment. The top of FIG. 2A shows a circuit in which acoustic wavefilter 11A and LC filter 12A included in radio frequency circuit 1 areconnected in series. The bottom graph drawing of FIG. 2A shows thepassing characteristics of acoustic wave filter 11A alone (the solidline), the passing characteristics of LC filter 12A alone (the brokenline), and the passing characteristics of the series circuit of acousticwave filter 11A and LC filter 12A (the alternate long and short dashline).

As illustrated in the bottom graph drawing of FIG. 2A, since acousticwave filter 11A includes a first acoustic wave resonator (e.g., a SAWresonator) having a high Q factor, the passing characteristics (SAW) ofacoustic wave filter 11A are that (1) there is low loss within apassband, and (2) since attenuation slopes at both ends of the passbandare steep, a large amount of attenuation in attenuation bands in aneighborhood of the passband can be ensured. On the other hand, (3)there is an attenuation band (a band in which attenuation rebounds) withan amount of attenuation that decreases with a distance from thepassband due to a rebound of high attenuation in the neighborhood of thepassband.

In contrast, since LC filter 12A includes an inductor and a capacitor,the passing characteristics (LC) of LC filter 12A are that (1) sinceattenuation slopes at both ends of a passband are gentle, an amount ofattenuation in attenuation bands in a neighborhood of the passband issmall, compared to the passing characteristics of acoustic wave filter11A. On the other hand, (2) there is low loss within the passband andthe passband width is relatively wide, and (3) wide and stableattenuation can be ensured in an attenuation band away from thepassband.

Regarding the passing characteristics (SAW+LC) of the series circuit ofacoustic wave filter 11A and LC filter 12A having the above-describedpassing characteristics, the attenuation band in the neighborhood of thepassband strongly reflects the passing characteristics of acoustic wavefilter 11A, and the attenuation band away from the passband stronglyreflects the passing characteristics of LC filter 12A.

In other words, connecting acoustic wave filter 11A and LC filter 12A inseries enables the series circuit to have the passing characteristics inwhich (i) low loss in a passband, (ii) high attenuation in aneighborhood of the passband, and (iii) high attenuation in a band awayfrom the passband are ensured. It should be noted that even a seriescircuit obtained by changing the series connection order of acousticwave filter 11A and LC filter 12A will have the passing characteristicsin which (i) to (iii) are ensured.

FIG. 2B is a diagram illustrating passing characteristics of radiofrequency circuit 1 according to the embodiment. The top of FIG. 2Bshows a circuit configured as radio frequency module 10 included inradio frequency circuit 1. The bottom graph drawing of FIG. 2B shows thepassing characteristics of acoustic wave filter 11A alone (the solidline on the low-frequency side), the passing characteristics of acousticwave filter 11B alone (the solid line on the high-frequency side), thepassing characteristics of LC filter 12A alone (the broken line on thelow-frequency side), the passing characteristics of LC filter 12B alone(the broken line on the high-frequency side), the passingcharacteristics of the series circuit of acoustic wave filter 11A and LCfilter 12A (the alternate long and short dash line on the low-frequencyside), and the passing characteristic of the series circuit of acousticwave filter 11B and LC filter 12B (the alternate long and short dashline on the high-frequency side).

It should be noted that in the present embodiment, the series circuit ofacoustic wave filter 11A and LC filter 12A passes radio frequencysignals in communication band A, and the series circuit of acoustic wavefilter 11B and LC filter 12B passes radio frequency signals incommunication band B. Here, it is assumed that communication band A hasa frequency range that does not overlap a frequency range ofcommunication band B, and communication band A is closer to thelow-frequency side than communication band B.

As illustrated in the bottom graph drawing of FIG. 2B, the seriescircuit of acoustic wave filter 11A and LC filter 12A have the passingcharacteristics in which low loss in a passband (communication band A),high attenuation in a neighborhood of the passband (communication bandA), and high attenuation in a band away from the passband (communicationband A) are ensured.

Further, the series circuit of acoustic wave filter 11B and LC filter12B have the passing characteristics in which low loss in a passband(communication band B), high attenuation in a neighborhood of thepassband (communication band B), and high attenuation in a band awayfrom the passband (communication band B) are ensured.

A comparative radio frequency circuit has a configuration in which amultiplexer that demultiplexes radio frequency signals in a firstfrequency band group including communication bands and radio frequencysignals in a second frequency band group including communication bandsis disposed upstream, and filters having respective communication bandsas passbands are disposed downstream. In this case, an LC filterfavorable for ensuring a wide passband that is a frequency band group isused as the multiplexer disposed upstream, and acoustic wave filtersfavorable for ensuring relatively narrow passbands that are therespective communication bands are used as the filters disposeddownstream.

Radio frequency circuit 1 according to the present embodiment has thesame passing characteristics of the series circuit alone including theacoustic wave filter and the LC filter as the comparative radiofrequency circuit. Radio frequency circuit 1, however, differs from thecomparative radio frequency circuit in that, when the front ends of twoseries circuits corresponding to different communication bands areconnected with a common terminal, a difference in passingcharacteristics of the multiplexer disposed upstream makes a significantdifference in propagation characteristics of radio frequency signals.

For example, in the fifth generation mobile communication system (5G) tobe introduced in the foreseeable future, a communication band has ahigher frequency and a wider bandwidth, and a frequency gap betweenadjacent communication bands is relatively small. When a communicationband has a wider bandwidth and a frequency gap between the adjacentcommunication bands is small as above, the propagation loss of radiofrequency signals is increased in the comparative radio frequencycircuit as described above.

For the purpose of describing the above, it is assumed that amultiplexer disposed upstream as a comparative radio frequency circuitincludes a first LC filter having a passband that is communication bandA and a second LC filter having a passband that is communication band B.In this case, although communication band A and communication band Bhave wide bandwidths, whereas a frequency gap between communication bandA and communication band B is relatively small, attenuation slopes inneighborhoods of the passbands of the first LC filter and the second LCfilter are less steep. For this reason, a radio frequency signal incommunication band A passes through the second LC filter withoutnecessarily selectively passing through the first LC filter due to asmall amount of attenuation in the neighborhood of the passband of thesecond LC filter. Likewise, a radio frequency signal in communicationband B passes through the first LC filter without necessarilyselectively passing through the second LC filter due to a small amountof attenuation in the neighborhood of the passband of the first LCfilter. In other words, since isolation between the adjacentcommunication bands deteriorates due to the lack of steepness of theattenuation slopes in the neighborhoods of the passbands of the LCfilters, in particular, the propagation loss of the radio frequencysignals in adjacent communication bands A and B is increased.

In contrast, since multiplexer 11 connected to common terminal 100includes acoustic wave filters 11A to 11D having highly steepattenuation slopes in neighborhoods of passbands, radio frequencycircuit 1 according to the present embodiment demultiplexes radiofrequency signals in communication band A and radio frequency signals incommunication band B with high isolation even when communication band Aand communication band B are relatively close to each other. Moreover,although acoustic wave filters 11A to 11D included in multiplexer 11each have a small amount of attenuation in a band (a band in whichattenuation rebounds) away from the passband, since LC filters 12A and12B each of which widely and stably ensures attenuation in the band awayfrom the passband are disposed downstream, radio frequency circuit 1highly attenuates the band away from the passband. Accordingly, radiofrequency circuit 1 demultiplexes radio frequency signals incommunication bands with high isolation and low loss.

3. Example of Usage for 5G NR

Radio frequency circuit 1 and communication device 5 according to thepresent embodiment can be used for 5G. For example, n79, having afrequency range from 4400 MHz to 5000 MHz, of New Radio (NR) is used ascommunication band B, and n77, having a frequency range from 3300 MHz to4200 MHz, of NR is used as communication band A. n79 has a bandwidth of600 MHz, and n77 has a bandwidth of 900 MHz. A frequency gap between n79and n77 is 200 MHz. In other words, compared to communication bandsspecified in 4G, communication bands specified in 5G have a widebandwidth and a frequency gap between adjacent ones of the communicationbands is small.

When n79 and n77 of 5G described as the example above are used in acomparative radio frequency circuit, a configuration in which a transfercircuit for n79 and a transfer circuit for n77 are connected to separateantenna elements is first conceivable as a means for ensuring highisolation. This makes it possible to transfer signals in n79 and n77having a small frequency gap with high isolation. Unfortunately, sincethe number of antenna elements increases, a communication device growsin size.

Moreover, a configuration in which an acoustic wave filter that uses oneantenna element and makes steeper attenuation slopes in a neighborhoodof a passband is disposed as a multiplexer in each of a transfer circuitfor n79 and a transfer circuit for n77 is conceivable as another meansfor ensuring high isolation. This makes it possible to ensure highisolation in a boundary area between n79 and n77 having a smallfrequency gap. However, since the acoustic wave filter has a smallamount of attenuation in a band (a band in which attenuation rebounds)away from the passband, for example, it is not possible to sufficientlyensure amounts of attenuation on a low-frequency side range in n77 and ahigh-frequency side range in n79. Accordingly, it is difficult to ensurehigh isolation over an entire band relative to radio frequency signalsin n77 and n79.

Furthermore, a configuration in which an LC filter that uses one antennaelement and attenuates a band away from a passband is disposed as amultiplexer in each of a transfer circuit for n79 and a transfer circuitfor n77 is conceivable as still another means for ensuring highisolation. In this case, as stated above, since isolation between theadjacent communication bands deteriorates due to the lack of steepnessof attenuation slopes in a neighborhood of the passband of the LCfilter, the propagation loss is increased.

In contrast, when radio frequency circuit 1 and communication device 5according to the present embodiment are used for 5G NR, the acousticwave filter disposed upstream ensures isolation in a boundary areabetween two communication bands having a small frequency gap, and the LCfilter disposed downstream ensures isolation over the entirety of a widecommunication band, and further highly attenuates an undesired signal inSub6 (a frequency range from 400 MHz to 7 GHz).

It should be noted that communication bands used in radio frequencycircuit 1 and communication device 5 according to the present embodimentare not limited to above n77 and n79.

For example, at least part of n79 of NR may be used as communicationband B, and at least one of at least part of n77 of NR, at least part ofn78, having a frequency range from 3300 MHz to 3800 MHz, of NR, B42,having a frequency range from 3400 MHz to 3600 MHz, of LTE, B43, havinga frequency range from 3600 MHz to 3800 MHz, of LTE, B48, having afrequency range from 3550 MHz to 3700 MHz, of LTE, or B49, having afrequency range from 3550 MHz to 3700 MHz, of LTE may be used ascommunication band A.

It should be noted that, for example, in n77 (3.3 GHz to 4.2 GHz) of NR,a frequency range of 3.6 to 4.1 GHz is allotted in Japan, and further asubdivided frequency range such as a frequency range of 3.7 to 3.8 GHzand a frequency range of 4.0 to 4.1 GHz is allocated to eachtelecommunications carrier. For this reason, each of communication bandsA and B may be equivalent to part of n77, n78, or n79 of NR.

In other words, at least one of acoustic wave filter 11A or acousticwave filter 11B may have a passband that is n79 of NR, and the other ofacoustic wave filters 11A and 11B may have a passband that is at leastone of n77 of NR, n78 of NR, B42 of LTE, B43 of LTE, B48 of LTE, or B49of LTE.

Accordingly, it is possible to transfer signals in communication bandsof 5G NR with high isolation and low loss, and further transfer signalsin the communication bands of 5G NR and communication bands of 4G LTEwith high isolation and low loss.

Moreover, for example, NR-U having a frequency range from 5.15 GHz to5.925 GHz may be used as communication band B, and NR having a frequencyrange from 4.4 GHz to 5.0 GHz less than or equal to 5 GHz may be used ascommunication band A.

Moreover, for example, NR-U having a frequency range from 5.47 GHz to5.925 GHz may be used as communication band B, and NR-U having afrequency range from 5.15 GHz to 5.35 GHz may be used as communicationband A.

Moreover, for example, NR-U having a frequency range from 5.925 GHz to7.125 GHz may be used as communication band B, and NR-U having afrequency range from 5.15 GHz to 5.85 GHz may be used as communicationband A.

It should be noted that NR-U is 5G-NR greater than or equal to 5 GHz in3GPP, and is equivalent to communication band U-NII in an unlicensedband allocated by the Federal Communications Commission (FCC).

In other words, (1) the first acoustic wave filter and the secondacoustic wave filter may have a passband that is a communication band ofNew Radio (NR) less than or equal to 5 GHz, (2) the first acoustic wavefilter may have a passband that is a communication band of NR less thanor equal to 5 GHz, and the second acoustic wave filter has a passbandthat is an unlicensed band of Long Term Evolution (LTE), NR, or WirelessLocal Area Network (WLAN) greater than or equal to 5 GHz, or (3) thefirst acoustic wave filter and the second acoustic wave filter may havea passband that is an unlicensed band of LTE, NR, or WLAN greater thanor equal to 5 GHz.

At least one of wireless LAN (2.4 GHz), wireless LAN (5 GHz)encompassing B46 and B47 of LTE, a low band group (617 to 960 MHz),GPS(registered trademark)-L1 (1559 to 1606 MHz), GPS-L5 (1166 to 1229MHz), a middle band group (1427 to 2200 MHz), a high band group (2300 to2690 MHz), or an ultrahigh band group (3300 to 4990 MHz) may be used aseach of passbands of acoustic wave filters 11C and 11D included inmultiplexer 11.

4. Passing Characteristics of Radio Frequency Circuit 6 According toVariation Embodiment 1

FIG. 3A is an example circuit configuration diagram illustrating radiofrequency circuit 6 and antenna element 2 according to Variationembodiment 1 of the embodiment. As illustrated in FIG. 3A, radiofrequency circuit 6 according to the present variation includes commonterminal 100, multiplexer 11, LC filters 12A and 12B, switch circuit 13,low-noise amplifiers 21A and 21B, and reception output terminals 110Aand 110B.

Radio frequency circuit 6 according to the present variation embodimentdiffers from radio frequency circuit 1 according to the presentembodiment only in that switch circuit 13 is added. In what follows, adescription of similarities in configuration between radio frequencycircuit 6 according to the present variation embodiment and radiofrequency circuit 1 according to the present embodiment is omitted, anddifferences in configuration therebetween are mainly described.

Switch circuit 13 is disposed between multiplexer 11 and LC filters 12Aand 12B, and includes switches 13A and 13B. Switch 13A is an example ofa first switch, is disposed between acoustic wave filter 11A and LCfilter 12A, and switches between making a connection and making adisconnection between acoustic wave filter 11A and LC filter 12A. Switch13A is, for example, a single-pole-single-throw (SPST) switch. Switch13B is an example of a second switch, is disposed between acoustic wavefilter 11B and LC filter 12B, and switches between making a connectionand making a disconnection between acoustic wave filter 11B and LCfilter 12B. Switch 13B is, for example, an SPST switch.

Switch circuit 13 puts a reception path on which acoustic wave filter11A and LC filter 12A are disposed and a reception path on whichacoustic wave filter 11B and LC filter 12B are disposed, into an OFFstate (a signal non-propagation state), according to a usage state ofcommunication bands.

5. Passing Characteristics of Radio Frequency Circuit 7 According toVariation Embodiment 2

FIG. 3B is an example of a circuit configuration diagram illustratingradio frequency circuit 7 and antenna element 2 according to Variationembodiment 2 of the embodiment. As illustrated in FIG. 3B, radiofrequency circuit 7 according to the present variation embodimentincludes common terminal 100, multiplexer 11, LC filters 12A and 12B,switch circuit 14, low-noise amplifiers 21A, 21B1, and 21B2, andreception output terminals 110A, 110B1, and 110B2.

Radio frequency circuit 7 according to the present variation embodimentdiffers from radio frequency circuit 1 according to the above embodimentin that low-noise amplifiers 21B1 and 21B2 are disposed in place oflow-noise amplifier 21B, and switch circuit 14 is added. In whatfollows, a description of similarities in configuration between radiofrequency circuit 7 according to the present variation embodiment andradio frequency circuit 1 according to the above embodiment is omitted,and differences in configuration therebetween are mainly described.

Low-noise amplifier 21A is an example of the first amplifier, and has aninput terminal connected to the output terminal of LC filter 12A viaterminal 160A, and an output terminal connected to reception outputterminal 110A. Low-noise amplifier 21A amplifies a received radiofrequency signal in communication band A that has been inputted fromcommon terminal 100 and has passed through acoustic wave filter 11A andLC filter 12A, and outputs the amplified radio frequency signal to RFIC3.

Low-noise amplifier 21B1 is an example of the second amplifier, and hasan input terminal connected to the output terminal of LC filter 12B viaswitch circuit 14, and an output terminal connected to reception outputterminal 110B1. Low-noise amplifier 21B1 amplifies a received radiofrequency signal in communication band B1 that has been inputted fromcommon terminal 100 and has passed through acoustic wave filter 11B andLC filter 12B, and outputs the amplified radio frequency signal to RFIC3.

Low-noise amplifier 21B2 is an example of the second amplifier, and hasan input terminal connected to the output terminal of LC filter 12B viaswitch circuit 14, and an output terminal connected to reception outputterminal 110B2. Low-noise amplifier 21B2 amplifies a received radiofrequency signal in communication band B2 that has been inputted fromcommon terminal 100 and has passed through acoustic wave filter 11B andLC filter 12B, and outputs the amplified radio frequency signal to RFIC3.

The series circuit of acoustic wave filter 11A and LC filter 12A passesradio frequency signals in communication band A, and the series circuitof acoustic wave filter 11B and LC filter 12B passes radio frequencysignals in communication band B.

Switch circuit 14 includes common terminal 14 a and selection terminals14 b 1 and 14 b 2, switches between making a connection and making adisconnection between LC filter 12B and low-noise amplifier 21B1, andswitches between making a connection and making |disconnection betweenLC filter 12B and low-noise amplifier 21B2. Switch circuit 14 is, forexample, a single-pole-single-throw (SPST) switch.

According to the above configuration, putting common terminal 14 a andselection terminal 14 b 1 into the connection state enables simultaneousreception of signals in communication band A and communication band B1,and putting common terminal 14 a and selection terminal 14 b 2 into theconnection state enables simultaneous reception of signals incommunication band A and communication band B2. Moreover, sincelow-noise amplifiers 21B1 and 21B2 amplify the radio frequency signal incommunication band B1 and the radio frequency signal in communicationband B2, respectively, it is possible to set the amplificationcharacteristics of low-noise amplifiers 21B1 and 21B2 exclusively forrespective communication bands B1 and B2. Accordingly, it is possible toenhance performance regarding the gain, distortion characteristics, andpower consumption of low-noise amplifiers 21B1 and 21B2.

Furthermore, radio frequency circuit 7 according to the presentvariation embodiment transfers radio frequency signals for 5G NR andradio frequency signals for 4G LTE.

For example, acoustic wave filter 11A and LC filter 12A have a passbandthat is n79 of NR, and acoustic wave filter 11B and LC filter 12B have apassband that is n77 of NR. Further, low-noise amplifier 21A hasamplification characteristics for amplifying radio frequency signals inn79, low-noise amplifier 21B1 has amplification characteristics foramplifying radio frequency signals in n77, and low-noise amplifier 21B2has amplification characteristics for amplifying a radio frequencysignal in B42. It should be noted that the frequency range of n77encompasses the frequency range of B42.

In the above example of usage, putting common terminal 14 a andselection terminal 14 b 1 into the connection state and putting commonterminal 14 a and selection terminal 14 b 2 into the connection stateenable simultaneous reception (EN-DC) of signals in n77 of 5G NR and B42of 4G LTE that have the frequency ranges in an encompassingrelationship.

6. Passing Characteristics of Radio Frequency Circuit 8 According toVariation Embodiment 3

FIG. 3C is a circuit configuration diagram illustrating radio frequencycircuit 8 and antenna element 2 according to Variation embodiment 3 ofthe embodiment. As illustrated in FIG. 3C, radio frequency circuit 8according to the present variation includes common terminal 100,multiplexer 11, LC filters 12A, 12B1, and 12B2, switch circuit 15,low-noise amplifiers 21A, 21B1, and 21B2, and reception output terminals110A, 110B1, and 110B2.

Radio frequency circuit 8 according to the present variation embodimentdiffers from radio frequency circuit 1 according to the presentembodiment in that low-noise amplifiers 21B1 and 21B2 are disposed inplace of low-noise amplifier 21B, LC filters 12B1 and 12B2 are disposedin place of LC filter 12B, and switch circuit 15 is added. In whatfollows, a description of similarities in configuration between radiofrequency circuit 8 according to the present variation embodiment andradio frequency circuit 1 according to the present embodiment isomitted, and differences in configuration therebetween are mainlydescribed.

LC filter 12A is an example of the first LC filter. Specifically, LCfilter 12A is a radio frequency filter that has an input terminalconnected to the output terminal of acoustic wave filter 11A viaconnection node n1, and an output terminal connected to terminal 160A,and that includes at least one of an inductor or a capacitor. LC filter12A has a passband that is communication band A.

LC filter 12B1 is an example of the second LC filter. Specifically, LCfilter 12B1 is a radio frequency filter that has an input terminalconnected to the output terminal of acoustic wave filter 11B via switchcircuit 15, and an output terminal connected to the input terminal oflow-noise amplifier 21B1, and that includes at least one of an inductoror a capacitor. LC filter 12B1 has a passband that is communication bandB 1.

LC filter 12B2 is an example of the second LC filter. Specifically, LCfilter 12B2 is a radio frequency filter that has an input terminalconnected to the output terminal of acoustic wave filter 11B via switchcircuit 15, and an output terminal connected to the input terminal oflow-noise amplifier 21B2, and that includes at least one of an inductoror a capacitor. LC filter 12B2 has a passband that is communication bandB2.

Low-noise amplifier 21A is an example of the first amplifier, and has aninput terminal connected to the output terminal of LC filter 12A viaterminal 160A, and an output terminal connected to reception outputterminal 110A. Low-noise amplifier 21A amplifies a received radiofrequency signal in communication band A that has been inputted fromcommon terminal 100 and has passed through acoustic wave filter 11A andLC filter 12A, and outputs the amplified radio frequency signal to RFIC3.

Low-noise amplifier 21B1 is an example of the second amplifier, and hasan input terminal connected to the output terminal of LC filter 12B1,and an output terminal connected to reception output terminal 110B1.Low-noise amplifier 21B1 amplifies a received radio frequency signal incommunication band B1 that has been inputted from common terminal 100and has passed through acoustic wave filter 11B and LC filter 12B1, andoutputs the amplified radio frequency signal to RFIC 3.

Low-noise amplifier 21B2 is an example of the second amplifier, and hasan input terminal connected to the output terminal of LC filter 12B2,and an output terminal connected to reception output terminal 110B2.Low-noise amplifier 21B2 amplifies a received radio frequency signal incommunication band B2 that has been inputted from common terminal 100and has passed through acoustic wave filter 11B and LC filter 12B2, andoutputs the amplified radio frequency signal to RFIC 3.

The series circuit of acoustic wave filter 11A and LC filter 12A passesradio frequency signals in communication band A. A series circuitincluding acoustic wave filter 11B and LC filter 12B1 connected viaswitch circuit 15 passes radio frequency signals in communication bandB1. A series circuit including acoustic wave filter 11B and LC filter12B2 connected via switch circuit 15 passes radio frequency signals incommunication band B2.

Switch circuit 15 includes common terminal 15 a and selection terminals15 b 1 and 15 b 2, switches between making a connection and making adisconnection between acoustic wave filter 11B and LC filter 12B1, andswitches between making a connection and making a disconnection betweenacoustic wave filter 11B and LC filter 12B2. Switch circuit 15 is, forexample, an SPST switch.

According to the above configuration, putting common terminal 15 a andselection terminal 15 b 1 into the connection state enables simultaneousreception of signals in communication band A and communication band B 1,and putting common terminal 15 a and selection terminal 15 b 2 into theconnection state enables simultaneous reception of signals incommunication band A and communication band B2. Moreover, sincelow-noise amplifiers 21B1 and 21B2 amplify the radio frequency signal incommunication band B1 and the radio frequency signal in communicationband B2, respectively, it is possible to set the amplificationcharacteristics of low-noise amplifiers 21B1 and 21B2 exclusively forrespective communication bands B1 and B2. Accordingly, it is possible toenhance performance regarding the gain, distortion characteristics, andpower consumption of low-noise amplifiers 21B1 and 21B2.

Furthermore, radio frequency circuit 8 according to the presentvariation transfers radio frequency signals for 5G NR and radiofrequency signals for 4G LTE.

For example, acoustic wave filter 11A and LC filter 12A have a passbandthat is n79 of NR, LC filter 12B1 has a passband that is n77 of NR, andLC filter 12B2 has a passband that is n78 of NR. For this reason,acoustic wave filter 11B has n77 and n78 of NR as passbands. Low-noiseamplifier 21A has amplification characteristics for amplifying radiofrequency signals in n79 of NR, low-noise amplifier 21B1 hasamplification characteristics for amplifying radio frequency signals inn77 of NR, and low-noise amplifier 21B2 has amplificationcharacteristics for amplifying radio frequency signals in n78 of NR. Itshould be noted that the frequency range of n78 of NR encompasses thefrequency ranges of B42, B43, and B49 of LTE.

In the above example of usage, putting common terminal 15 a andselection terminal 15 b 2 into the connection state enables simultaneousreception (EN-DC) of signals in n79 of 5G NR and B42, B43, B48, or B49of 4G LTE.

7. Structure of Acoustic Wave Filter and LC Filter

FIG. 4A is a diagram illustrating the first example of a circuitconfiguration of acoustic wave filter 11A according to the embodiment.As illustrated in FIG. 4A, acoustic wave filter 11A includes series-armresonators s1, s2, s3, and s4, parallel-arm resonators p1, p2, and p3,and inductors L1 and L2.

Series-arm resonators s1 to s4 are each an example of the first acousticwave resonator, and are arranged in series on a path connecting commonterminal 100 and connection node n1. Parallel-arm resonators p1 to p3are each an example of the first acoustic wave resonator, and aredisposed between ground and nodes on the path connecting series-armresonators s1 to s4 and connection node n1.

Series-arm resonators s1 to s4 and parallel-arm resonators p1 to p3 eachhave a resonant frequency that causes impedance to have a local minimum,and an antiresonant frequency that causes an impedance to have a localmaximum. A passband of acoustic wave filter 11A is determined bysubstantially matching the antiresonant frequencies of parallel-armresonators p1 to p3 and the resonant frequencies of series-armresonators s1 to s4. It should be noted that there may be any number ofseries-arm resonators and any number of parallel-arm resonators. Inother words, acoustic wave filter 11A is configured as a ladder bandpassfilter including acoustic wave resonators. It should be noted thatacoustic wave filter 11A is not limited to the ladder bandpass filter,and may be a longitudinally coupled filter.

Inductor L1 is connected between parallel-arm resonator p1 and theground, and is a passive element for adjusting an attenuation pole in anattenuation band of acoustic wave filter 11A. Inductor L2 is connectedbetween connection node n1 and the ground, and is a passive element foradjusting an attenuation pole in an attenuation band of acoustic wavefilter 11A or for performing impedance matching between a circuitelement connected to connection node n1 and acoustic wave filter 11A. Itshould be noted that a capacitor may be disposed in place of inductorsL1 and L2, and further both an inductor and a capacitor may be disposedin place of the same.

In other words, the passband of acoustic wave filter 11A in the presentvariation embodiment is determined by only parallel-arm resonators p1 top3 and series-arm resonators s1 to s4. In contrast, the attenuation bandof acoustic wave filter 11A in the present variation embodiment isdetermined by parallel-arm resonators p1 to p3, series-arm resonators s1to s4, and inductors L1 and L2.

The above structure enables miniaturization and reduction in cost ofmultiplexer 11 including acoustic wave filter 11A.

It should be noted that in acoustic wave filter 11A in the presentvariation, a switch may be connected to at least one of the acousticwave resonators or inductors L1 and L2. In this case, for example, byswitching the switch according to a switch of a communication band to beused, it is possible to change the passband of acoustic wave filter 11A.

Moreover, acoustic wave filter 11A in the present variation embodimentdoes not necessarily need include inductors L1 and L2, and may includeonly the acoustic wave resonators.

Furthermore, acoustic wave filters 11B to 11D may each have thestructure of the present variation. Since the structure of acoustic wavefilters 11A to 11D enables multiplexer 11 to be integrated into onepiezoelectric substrate, the miniaturization is promoted.

FIG. 4BA is a diagram illustrating the second example of a circuitconfiguration and FIG. 4BB is an example graph diagram showing passingcharacteristics of acoustic wave filter 11A according to the embodiment.FIG. 4BA illustrates a circuit configuration of acoustic wave filter 11Ain the present variation embodiment (as shown in the upper part), andpassing characteristics of acoustic wave filter 11A in the presentvariation embodiment (as shown in the bottom part). As shown in FIG.4BA, acoustic wave filter 11A includes series-arm resonators s5 and s6,parallel-arm resonator p4, inductor L3, and matching circuit 18.

Series-arm resonators s5 and s6 are connected in series between commonterminal 100 and connection node n1.

Parallel-arm resonator p4 is connected between the ground and connectionnode xl between series-arm resonators s5 and s6.

Inductor L3 is connected between a connection node between series-armresonator s5 and common terminal 100 and a connection node betweenseries-arm resonator s6 and matching circuit 18. Matching circuit 18 isconnected between series-arm resonator s6 and connection node n1.

Series-arm resonators s5 and s6 and inductor L3 constitute LC resonantcircuit 16. Further, series-arm resonators s5 and s6 and parallel-armresonator p4 determine a passband of bandpass filter 17.

In the FIG. 4BB, attenuation pole Z2 corresponds to a resonant frequencyof parallel-arm resonator p4, attenuation pole Z3 corresponds to anantiresonant frequency of series-arm resonator s5, and attenuation poleZ4 corresponds to an antiresonant frequency of series-arm resonator s6.Series-arm resonators s5 and s6 and parallel-arm resonator p4 operate asa notch filter. Attenuation pole Z2 and attenuation poles Z3 and Z4 forma low-frequency side attenuation slope and a high-frequency sideattenuation slope of the passband of acoustic wave filter 11A,respectively. A passband of LC resonant circuit 16 has, for example, afractional bandwidth of at least 4.5%, and ranges from a frequencycorresponding to attenuation pole Z2 to a frequency corresponding toattenuation pole Z4. However, since the antiresonant frequency of eachof series-arm resonators s5 and s6 and the resonant frequency ofparallel-arm resonator p4 are located in the passband, the passband islocally attenuated. It should be noted that since series-arm resonatorss5 and s6 and parallel-arm resonator p4 each are an acoustic waveresonator, the attenuation slopes of these are steep. Here, by locatingattenuation pole Z2 and attenuation poles Z3 and Z4 away from each other(i.e., locating the anti-resonant frequencies of series-arm resonatorss5 and s6 and the resonant frequency of parallel-arm resonator p4 awayfrom each other), acoustic wave filter 11A can be used as a bandpassfilter having passing characteristics in which a passband is wide. Itshould be noted that a wide passband has, for example, a fractionalbandwidth of at least 4.5%, and desirably a fractional bandwidth of atleast 7.5%. Further, LC resonant circuit 16 has a lower resonantfrequency than parallel-arm resonator p4. Attenuation pole Z1corresponds to a resonant frequency of LC resonant circuit 16.Accordingly, it is possible to increase the width of an attenuation bandlower than the passband of acoustic wave filter 11A. It should be notedthat, by adjusting an inductance value of inductor L3, it is possible toadjust the resonant frequency of LC resonant circuit 16, and locate theattenuation poles of LC resonant circuit 16 away from the passband ofacoustic wave filter 11A.

In other words, acoustic wave filter 11A in the present variationembodiment may include at least one of an inductor or a capacitor inaddition to the acoustic wave resonators. According to thisconfiguration, a passband is determined by LC resonant circuit 16, andattenuation poles defining the bandwidth of the passband are determinedby the acoustic wave resonators. In addition, an attenuation pole in anattenuation band away from the passband is determined by LC resonantcircuit 16. As a result, it is possible to achieve a wide and low-losspassband, and steeply attenuate a neighborhood of the passband.

It should be noted that in acoustic wave filter 11A in the presentvariation embodiment, a switch may be disposed in at least one of LCresonant circuit 16 or bandpass filter 17. In this case, for example, byswitching the switch according to a switch of a communication band to beused, it is possible to change the passband of acoustic wave filter 11A.

Furthermore, acoustic wave filters 11B to 11D may each have thestructure of the present variation embodiment.

FIG. 4C is a diagram illustrating an example of a circuit configurationof LC filter 12A according to the embodiment. As illustrated in FIG. 4C,LC filter 12A includes capacitors C1, C2, C3, C4, C5, C6, C7, and C8 andinductors L4, L5, L6, and L7.

Capacitor C1, capacitor C2, a parallel circuit of inductor L4 andcapacitor C3, and a parallel circuit of inductor L5 and capacitor C4 areconnected in series on a path connecting connection node n1 and terminal160A. A series circuit of inductor L6 and capacitor C5, a series circuitof inductor L7 and capacitor C6, capacitor C7, and capacitor C8 aredisposed between ground and nodes on the path connecting connection noden1 and terminal 160A.

Inductor L4 and capacitor C3 constitute an LC parallel resonant circuit.Inductor L5 and capacitor C4 constitute an LC parallel resonant circuit.Inductor L6 and capacitor C5 constitute an LC series resonant circuit.Inductor L7 and capacitor C6 constitute an LC series resonant circuit.

A passband and an attenuation band of LC filter 12A are determined byadjusting resonant frequencies of the LC parallel resonant circuits andresonant frequencies of the LC series resonant circuits. It should benoted that although there may be any number of inductors and capacitorsand any connection relationship between those, it is desirable that LCfilter 12A include at least one of the LC parallel resonant circuits orthe LC series resonant circuits. In consequence, since it is possible touse an LC series resonant frequency or an LC parallel resonant frequencyas an attenuation pole, it is possible to achieve a wider attenuationband.

It should be noted that in LC filter 12A in the present variationembodiment, a switch may be connected to at least one of an inductor ora capacitor. In this case, for example, by switching the switchaccording to a switch of a communication band to be used, it is possibleto change the passband of LC filter 12A.

It should be noted that in the radio frequency circuit according to eachof the present embodiment and variations thereof, an impedance in thepassband of acoustic wave filter 11A seen from connection node n1 (anoutput impedance in the passband of acoustic wave filter 11A) and animpedance in the passband of LC filter 12A seen from connection node n1(an input impedance in the passband of LC filter 12A) may be matched atnon-50Ω.

When the output impedance of acoustic wave filter 11A has an impedancevalue of non-50Ω, since the input impedance of LC filter 12A isapproximately the same as the impedance value, it is not necessary todispose an impedance-matching circuit between acoustic wave filter 11Aand LC filter 12A.

Accordingly, it is possible to achieve the low loss in the passband forthe radio frequency signal passing through acoustic wave filter 11A andLC filter 12A and the high attenuation in the attenuation band whilesimplifying the impedance-matching element disposed between acousticwave filter 11A and LC filter 12A.

It should be noted that in radio frequency circuit 1 according to thepresent embodiment, an impedance in the passband of acoustic wave filter11B seen from connection node n2 (an output impedance in the passband ofacoustic wave filter 11B) and an impedance in the passband of LC filter12B seen from connection node n2 (an input impedance in the passband ofLC filter 12B) may be matched at non-50Ω.

FIG. 5 is an example of a circuit configuration diagram illustrating aneighborhood of connection node n1 between acoustic wave filter 11A andLC filter 12A of the radio frequency circuit according to theembodiment. As illustrated in FIG. 5 , when acoustic wave filter 11Aincludes one or more series-arm resonators and one or more parallel-armresonators, among the one or more series-arm resonators and the one ormore parallel-arm resonators, series-arm resonator s170 may be connectedclosest to connection node n1. In contrast, among inductors andcapacitors included in LC filter 12A, capacitor C170 may be connected inseries to series-arm resonator s170 via connection node n1. In otherwords, series-arm resonator s170 and capacitor C170 may be connected inseries via connection node n1.

Accordingly, an output impedance of acoustic wave filter 11A becomescapacitive, and so does an input impedance of LC filter 12A.Consequently, it is possible to easily match an impedance of acousticwave filter 11A with an impedance of LC filter 12A, using a few numberof impedance-matching elements with capacitive impedance.

It should be noted that when acoustic wave filter 11A and LC filter 12Aare impedance-matched at non-50Ω, acoustic wave filter 11A and LC filter12A may be disposed on the same substrate. When acoustic wave filter 11Aand LC filter 12A are impedance-matched at non-50Ω, it is not necessaryto dispose an impedance-matching element between acoustic wave filter11A and LC filter 12A. Accordingly, since acoustic wave filter 11A andLC filter 12A can be connected directly, it is easy to dispose thesefilters on the same substrate, which promotes the miniaturization ofradio frequency circuit 1.

Moreover, when acoustic wave filter 11A includes one or more series-armresonators and one or more parallel-arm resonators, among the one ormore series-arm resonators and the one or more parallel-arm resonators,a parallel-arm resonator may be connected closest to connection node n1.In contrast, among inductors and capacitors included in LC filter 12A, acapacitor may be connected between connection node n1 and ground, andmay be connected closest to connection node n1.

Accordingly, it is possible to easily match an impedance of acousticwave filter 11A with an impedance of LC filter 12A, using a few numberof impedance-matching elements with capacitive impedance.

8. Example of Passing Characteristics of Radio Frequency Circuit 1

FIG. 6A is an example of a circuit configuration diagram in which radiofrequency circuit 1 according to the embodiment is used forcommunication bands of 4G LTE and 5G NR, and graphs showing passingcharacteristics. FIG. 6A shows a circuit configured as radio frequencymodule 10 included in radio frequency circuit 1. Acoustic wave filter11A and LC filter 12A have a passband that is n79 of NR, and acousticwave filter 11B and LC filter 12B have a passband that is n77 of NRencompassing n78 of NR and B42, B43, B48, and B49 of LTE. FIG. 6B showspassing characteristics of acoustic wave filter 11B, FIG. 6C showspassing characteristics of LC filter 12B, and FIG. 6D shows passingcharacteristics of a series circuit of acoustic wave filter 11B and LCfilter 12B.

As shown in FIG. 6B, in the passing characteristics of acoustic wavefilter 11B, (1) there is low loss within the passband (3300 to 4200MHz), and (2) since attenuation slopes at both ends of the passband aresteep, a large amount of attenuation in attenuation bands in aneighborhood of the passband is ensured. On the other hand, (3) there isan attenuation band (a band in which attenuation rebounds) with anamount of attenuation that decreases with distance from the passbandtoward the high-frequency side due to a rebound of high attenuation inthe neighborhood of the passband.

In contrast, as shown in FIG. 6B, in the passing characteristics of LCfilter 12B, (1) since attenuation slopes at both ends of the passband(3300 to 4200 MHz) are gentle, an amount of attenuation in anattenuation band in a neighborhood of the passband is small, compared tothe passing characteristics of acoustic wave filter 11B. On the otherhand, (2) there is low loss within the passband, (3) the passband widthis relatively wide, and (4) wide and stable attenuation are ensured inan attenuation band away from the passband.

In contrast, as shown in FIG. 6C, in the passing characteristics of theseries circuit of acoustic wave filter 11B and LC filter 12B, highattenuation in a neighborhood of the passband strongly reflects thepassing characteristics of acoustic wave filter 11B, high attenuation onthe high-frequency side away from the passband strongly reflects thepassing characteristics of LC filter 12B, and wide and stableattenuation is ensured.

In other words, connecting acoustic wave filter 11B and LC filter 12B inseries enables the series circuit to have passing characteristics inwhich low loss in a wide passband of 900 MHz, high attenuation in theneighborhood of the passband, and high attenuation in a band away fromthe passband are ensured.

Moreover, a series circuit of acoustic wave filter 11A and LC filter 12Ais also capable of having passing characteristics in which low loss in awide passband (e.g., a pass band from 4400 MHz to 5000 MHz: a bandwidthof 600 MHz) that is n79 of NR, high attenuation in the neighborhood ofthe passband, and high attenuation in a band away from the passband areensured.

The radio frequency circuit according to each of the present embodimentand variations thereof makes it possible to transfer signals incommunication bands of 5G NR with high isolation and low loss, andfurther transfer signals in the communication bands of 5G NR andcommunication bands of 4G LTE with high isolation and low loss.

9. Configuration of Radio Frequency Circuit According to VariationEmbodiment 4

FIG. 7 is a circuit configuration diagram illustrating a radio frequencycircuit according to Variation embodiment 4 of the embodiment, andperipheral circuitry thereof. The radio frequency circuit according tothe present variation embodiment does not necessarily include commonterminal 100, multiplexer 11, LC filter 12B, and low-noise amplifier21B, compared to radio frequency circuit 1 according to the embodiment.

In other words, the radio frequency circuit according to the presentvariation embodiment includes LC filter 12A and low-noise amplifier 21A.

LC filter 12A is an example of the first LC filter, and is a highfrequency filter that has an output terminal connected to an inputterminal of low-noise amplifier 21A and includes at least one of aninductor or a capacitor. It should be noted that LC filter 12A includesno acoustic wave resonator.

Low-noise amplifier 21A is an example of a first low-noise amplifier,and has an input terminal connected to the output terminal of LC filter12A via terminal 160A.

According to the above configuration, since the input terminal oflow-noise amplifier 21A is connected to LC filter 12A having a wideattenuation band, a radio frequency signal from which unwanted wide-bandcomponents have been removed is inputted to low-noise amplifier 21A. Asa result, it is possible to greatly increase the S/N ratio of the radiofrequency signal outputted from low-noise amplifier 21A.

The radio frequency circuit according to the present variationembodiment may further include LC filter 12B and low-noise amplifier21B.

LC filter 12B is an example of the second LC filter, and is a highfrequency filter that has an output terminal connected to an inputterminal of low-noise amplifier 21B and includes at least one of aninductor or a capacitor. It should be noted that LC filter 12B includesno acoustic wave resonator.

Low-noise amplifier 21B is an example of a second low-noise amplifier,and has an input terminal connected to the output terminal of LC filter12B via terminal 160B.

Further, the input terminal of LC filter 12A and the input terminal ofLC filter 12B are connected to multiplexer 11 that demultiplexes a radiofrequency signal from antenna element 2.

Accordingly, unwanted wide-band components are removed from a radiofrequency signal to be outputted from multiplexer 11, and the radiofrequency signal is demultiplexed and inputted to low-noise amplifiers21A and 21B. As a result, it is possible to greatly increase the S/Nratio of the radio frequency signal outputted from low-noise amplifier21A and the S/N ratio of the radio frequency signal outputted fromlow-noise amplifier 21B.

The radio frequency circuit according to the present variationembodiment may further include acoustic wave filter 11A.

Acoustic wave filter 11A is an example of the first acoustic wavefilter, and is a radio frequency filter that has an output terminalconnected to the input terminal of LC filter 12A via connection node n1and includes the first acoustic wave resonator. The first acoustic waveresonator is, for example, an acoustic wave resonator that uses SAWs orBAWs.

Accordingly, since acoustic wave filter 11A capable of highlyattenuating the neighborhood of the passband due to the steepattenuation slopes at both ends of the passband is connected to thefront end of LC filter 12A, the radio frequency signal from whichunwanted wide-band components and unwanted components of theneighborhood of the passband have been removed is inputted to low-noiseamplifier 21A. As a result, it is possible to greatly increase the S/Nratio of the radio frequency signal outputted from low-noise amplifier21A.

It should be noted that LC filter 12A and low-noise amplifier 21A may bedisposed on the same substrate and constitute radio frequency module 50.Moreover, LC filters 12A and 12B and low-noise amplifiers 21A and 21Bmay be disposed on the same substrate and constitute radio frequencymodule 50. Accordingly, it is possible to achieve a small radiofrequency circuit.

10. Advantageous Effects, Etc

As described above, according to the present embodiment, radio frequencycircuit 1 includes acoustic wave filter 11A that is connected to commonterminal 100 and includes a first acoustic wave resonator, LC filter 12Athat is connected to common terminal 100 via acoustic wave filter 11Aand includes at least one of an inductor or a capacitor, acoustic wavefilter 11B that is connected to common terminal 100 and includes asecond acoustic wave resonator, and LC filter 12B that is connected tocommon terminal 100 via the second acoustic wave filter and includes atleast one of an inductor or a capacitor.

With this configuration, the acoustic wave filters used as multiplexer11 connected to common terminal 100 make it possible to demultiplexsignals in communication bands adjacent to a passband with highisolation, and highly attenuate neighboring bands of the passband.Further, LC filter 12A connected to acoustic wave filter 11A and LCfilter 12B connected to acoustic wave filter 11B make it possible tohighly attenuate bands away from the passband. Accordingly, it ispossible to demultiplex radio frequency signals in communication bandswith high isolation and low loss.

Moreover, according to the present embodiment, radio frequency circuit 1may further include: low-noise amplifier 21A that is connected to LCfilter 12A and amplifies a radio frequency signal; and low-noiseamplifier 21B that is connected to LC filter 12B and amplifies a radiofrequency signal.

With this configuration, it is possible to demultiplex and amplify aradio frequency signal inputted from common terminal 100.

Moreover, according to Variation embodiment 1 of the present embodiment,radio frequency circuit 6 may further include switch circuit 13. Switchcircuit 13 includes: switch 13A that is disposed between acoustic wavefilter 11A and LC filter 12A, and switches between making a connectionand making a disconnection between acoustic wave filter 11A and LCfilter 12A; and switch 13B that is disposed between acoustic wave filter11B and LC filter 12B, and switches between making a connection andmaking a disconnection between acoustic wave filter 11B and LC filter12B.

With this configuration, it is possible to put a first signal path onwhich acoustic wave filter 11A and LC filter 12A are disposed and asecond signal path on which acoustic wave filter 11B and LC filter 12Bare disposed, into an OFF state (a non-propagation state).

Moreover, according to the present embodiment, a passband of at leastone of acoustic wave filter 11A or 11B may be determined by only anacoustic wave resonator.

With this configuration, it is possible to miniaturize and reduce thecost of radio frequency circuit 1 and communication device 5.

Moreover, according to the present embodiment, at least one of acousticwave filter 11A or 11B may further include at least one of an inductoror a capacitor.

With this configuration, it is possible to achieve a wide and low-losspassband, and steeply attenuate an attenuation band in a neighborhood ofthe passband.

Moreover, according to the present embodiment, at least one of LC filter12A or 12B may include at least one of an LC series resonant circuit oran LC parallel resonant circuit.

With this configuration, it is possible to achieve a wider attenuationband by using an LC series resonant frequency or an LC parallel resonantfrequency as an attenuation pole.

Moreover, according to the present embodiment, impedance of acousticwave filter 11A seen from an LC filter 12A side and impedance of LCfilter 12A seen from an acoustic wave filter 11A side may be matched atnon-50Ω.

With this configuration, it is possible to achieve low loss in apassband for a radio frequency signal passing through acoustic wavefilter 11A and LC filter 12A and high attenuation in an attenuation bandwhile simplifying an impedance-matching element disposed betweenacoustic wave filter 11A and LC filter 12A.

Moreover, according to the present embodiment, acoustic wave filter 11Amay include: one or more series-arm resonators that are connected inseries on a path connecting an input terminal and an output terminal ofacoustic wave filter 11A; and one or more parallel-arm resonators thatare connected between the path and ground. Among the one or moreseries-arm resonators and the one or more parallel-arm resonators, aseries-arm resonator may be connected closest to LC filter 12A. Out ofan inductor and a capacitor included in LC filter 12A, the capacitor maybe connected closest to acoustic wave filter 11A.

With this configuration, it is possible to easily achieve impedancematching between capacitive acoustic wave filter 11A and LC filter 12Ausing a few number of impedance-matching elements.

Moreover, according to the present embodiment, acoustic wave filter 11Amay include: one or more series-arm resonators that are connected inseries on a path connecting an input terminal and an output terminal ofacoustic wave filter 11A; and one or more parallel-arm resonators thatare connected between the path and ground. Among the one or moreseries-arm resonators and the one or more parallel-arm resonators, aparallel-arm resonator may be connected closest to LC filter 12A. Out ofan inductor and a capacitor included in LC filter 12A, the capacitor maybe connected between the ground and a path connecting an input terminaland an output terminal of LC filter 12A, and may be connected closest toacoustic wave filter 11A.

With this configuration, it is possible to easily achieve impedancematching between capacitive acoustic wave filter 11A and LC filter 12Ausing a few number of impedance-matching elements.

Moreover, according to the present embodiment, acoustic wave filter 11Aand LC filter 12A may be disposed on a same substrate.

With this configuration, it is easy to perform impedance matchingbetween acoustic wave filter 11A and LC filter 12A while miniaturizingradio frequency circuit 1.

Moreover, according to the present embodiment, acoustic wave filters 11Aand 12A and LC filters 12A and 12B may be disposed on a same substrate.

With this configuration, it is possible to miniaturize radio frequencycircuit 1.

Moreover, according to the present embodiment, one of acoustic wavefilters 11A and 11B may have a passband that is n79 of NR, and the otherof acoustic wave filters 11A and 11B may have a passband that is atleast one of n77 of NR, n78 of NR, B42 of LTE, B43 of LTE, B48 of LTE,or B49 of LTE.

With this configuration, it is possible to transfer signals incommunication bands of 5G NR with high isolation and low loss, andfurther transfer signals in the communication bands of 5G NR andcommunication bands of 4G LTE with high isolation and low loss.

Moreover, according to Variation embodiment 1 of the present embodiment,the radio frequency circuit includes: LC filter 12A that includes noacoustic wave resonator and includes at least one of an inductor or acapacitor; and low-noise amplifier 21A that amplifies a radio frequencysignal. LC filter 12A has an output terminal connected to an inputterminal of low-noise amplifier 21A.

With this configuration, since the input terminal of low-noise amplifier21A is connected to LC filter 12A having a wide attenuation band, aradio frequency signal from which unwanted wide-band components havebeen removed is inputted to low-noise amplifier 21A. As a result, it ispossible to greatly increase the S/N ratio of the radio frequency signaloutputted from low-noise amplifier 21A.

Moreover, according to Variation embodiment 1 of the present embodiment,the radio frequency circuit may further include: LC filter 12B thatincludes no acoustic wave resonator and includes at least one of aninductor or a capacitor; and low-noise amplifier 21B that amplifies aradio frequency signal. LC filter 12B may have an output terminalconnected to an input terminal of low-noise amplifier 21B. LC filter 12Aand LC filter 12B may each have an input terminal connected tomultiplexer 11 that demultiplexes a radio frequency signal from antennaelement 2.

With this configuration, unwanted wide-band components are removed froma radio frequency signal to be outputted from multiplexer 11, and theradio frequency signal is demultiplexed and inputted to low-noiseamplifiers 21A and 21B. As a result, it is possible to greatly increasethe S/N ratio of the radio frequency signal outputted from low-noiseamplifier 21A and the S/N ratio of the radio frequency signal outputtedfrom low-noise amplifier 21B.

Moreover, according to Variation embodiment 1 of the present embodiment,the radio frequency circuit may further include acoustic wave filter 11Athat includes a first acoustic wave resonator. LC filter 12A may have aninput terminal connected to an output terminal of acoustic wave filter11A.

With this configuration, since acoustic wave filter 11A capable ofsteeply attenuating a neighboring band of a passband is connected to thefront end of LC filter 12A, a radio frequency signal from which unwantedwide-band components and unwanted components of a neighborhood of thepassband have been removed is inputted to low-noise amplifier 21A. As aresult, it is possible to greatly increase the S/N ratio of the radiofrequency signal outputted from low-noise amplifier 21A.

Moreover, according to the present embodiment, communication device 5includes RFIC 3 that processes a radio frequency signal received byantenna element 2, and radio frequency circuit 1 that transfers theradio frequency signal between antenna element 2 and RFIC 3.

With this configuration, it is possible to provide a communicationdevice that demultiplexes radio frequency signals in communication bandswith high isolation and low loss.

Other Embodiments

Although the radio frequency circuit and the communication deviceaccording to the present disclosure have been described using theembodiment and the variation embodiments, the present disclosure is notlimited to the afore-mentioned embodiment and variation embodiments. Thepresent disclosure contains other embodiments realized by combining anyelements in the afore-mentioned embodiment and variation embodiments,variation embodiments obtained by making various modifications to theafore-mentioned embodiment and variations that can be conceived by aperson with an ordinary skill in the art without departing from thescope of the present disclosure, and various devices that include theradio frequency circuit and the communication device according to thepresent disclosure.

For example, in the radio frequency circuit and the communication deviceaccording to each of the embodiment and the variation embodiments,matching elements such as inductors and capacitors, and switch circuitsmay be connected between the elements. Note that the inductor mayinclude a line inductor achieved by a line that connects elements.

Although only some exemplary embodiments of the present disclosure havebeen described in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of the present disclosure. Accordingly, all suchmodifications are intended to be included within the scope of thepresent disclosure.

The embodiments according to the present disclosure can be widely usedin communication apparatuses such as mobile phones, as radio frequencycircuits and communication devices that can be used in multi-bandsystems.

1. A radio frequency circuit, comprising: a substrate; a commonterminal; a first acoustic wave filter that is disposed on thesubstrate, is connected to the common terminal, and includes a firstacoustic wave resonator; a first LC filter that is disposed on thesubstrate, is connected to the common terminal via the first acousticwave filter, and includes at least one of an inductor or a capacitor; asecond acoustic wave filter that is disposed on the substrate, isconnected to the common terminal, and includes a second acoustic waveresonator; a second LC filter that is disposed on the substrate, isconnected to the common terminal via the second acoustic wave filter,and includes at least one of an inductor or a capacitor; a firstamplifier that is connected to the first LC filter and is disposed onthe substrate; and a second amplifier that is connected to the second LCfilter and is disposed on the substrate, wherein at least one of apassband of the first acoustic wave filter or a passband of the secondacoustic wave filter is a communication band of New Radio (NR).
 2. Theradio frequency circuit according to claim 1, further comprising: aswitch circuit, wherein: the switch circuit includes: a first switchthat is disposed between the first acoustic wave filter and the first LCfilter, and is configured to switch between making a connection andmaking a disconnection between the first acoustic wave filter and thefirst LC filter; and a second switch that is disposed between the secondacoustic wave filter and the second LC filter, and is configured toswitch between making a connection and making a disconnection betweenthe second acoustic wave filter and the second LC filter.
 3. The radiofrequency circuit according to claim 1, wherein: the passband of atleast one of the first acoustic wave filter or the second acoustic wavefilter is determined by only an acoustic wave resonator.
 4. The radiofrequency circuit according to claim 1, wherein: at least one of thefirst acoustic wave filter or the second acoustic wave filter furtherincludes at least one of an inductor or a capacitor.
 5. The radiofrequency circuit according to claim 1, wherein: at least one of thefirst LC filter or the second LC filter includes at least one of an LCseries resonant circuit or an LC parallel resonant circuit.
 6. The radiofrequency circuit according to claim 1, wherein: an impedance of thefirst acoustic wave filter seen from a first LC filter side and animpedance of the first LC filter seen from a first acoustic wave filterside are matched at non-50 Ω.
 7. The radio frequency circuit accordingto claim 1, wherein: the first acoustic wave filter includes: one ormore series-arm resonators that are connected in series on a pathconnecting an input terminal and an output terminal of the firstacoustic wave filter; and one or more parallel-arm resonators that areconnected between the path and ground, among the one or more series-armresonators and the one or more parallel-arm resonators, one of theseries-arm resonators is connected closest to the first LC filter, andout of an inductor and a capacitor included in the first LC filter, thecapacitor is connected closest to the first acoustic wave filter.
 8. Theradio frequency circuit according to claim 1, wherein: the firstacoustic wave filter includes: one or more series-arm resonators thatare connected in series on a path connecting an input terminal and anoutput terminal of the first acoustic wave filter; and one or moreparallel-arm resonators that are connected between the path and ground,among the one or more series-arm resonators and the one or moreparallel-arm resonators, a parallel-arm resonator is connected closestto the first LC filter, and out of an inductor and a capacitor includedin the first LC filter, the capacitor is connected between the groundand a path connecting an input terminal and an output terminal of thefirst LC filter, and is connected closest to the first acoustic wavefilter.
 9. The radio frequency circuit according to claim 1, wherein:the first acoustic wave filter and the first LC filter are disposed on asame substrate.
 10. The radio frequency circuit according to claim 1,wherein: the first acoustic wave filter, the first LC filter, the secondacoustic wave filter, and the second LC filter are disposed on a samesubstrate.
 11. The radio frequency circuit according to claim 1,wherein: (1) the passbands of the first acoustic wave filter and thesecond acoustic wave filter are communication bands of New Radio (NR)less than or equal to 5 GHz, or (2) the passband of the first acousticwave filter is a communication band of NR less than or equal to 5 GHzand the passband of the second acoustic wave filter is an unlicensedband of Long Term Evolution (LTE), NR, or Wireless Local Area Network(WLAN) greater than or equal to 5 GHz, or (3) the passbands of the firstacoustic wave filter and the second acoustic wave filter are unlicensedbands of LTE, NR, or WLAN greater than or equal to 5 GHz.
 12. The radiofrequency circuit according to claim 1, wherein: the passband of thefirst acoustic wave filter is NR, having a frequency range from 4.4 GHzto 5.0 GHz, and the passband of the second acoustic wave filter is NR-Uwith a frequency range from GHz to 5.925 GHz.
 13. The radio frequencycircuit according to claim 1, wherein: the passband of the firstacoustic wave filter is NR-U with a frequency range from 5.15 GHz to5.35 GHz, and the passband of the second acoustic wave filter is NR-Uwith a frequency range from GHz to 5.925 GHz.
 14. The radio frequencycircuit according to claim 1, wherein: the passband of the firstacoustic wave filter is NR-U with a frequency range from 5.15 GHz to5.85 GHz, and the passband of the second acoustic wave filter is NR-Uwith a frequency range from GHz to 7.125 GHz.
 15. The radio frequencycircuit according to claim 1, wherein: one of the passband of the firstacoustic wave filter and the passband of the second acoustic wave filteris at least part of n79, having a frequency range from 4400 MHz to 5000MHz, of New Radio (NR), and the other of the passband of the firstacoustic wave filter and the passband of the second acoustic wave filteris at least one of at least part of n77, having a frequency range from3300 MHz to 4200 MHz, of NR, at least part of n78, having a frequencyrange from 3300 MHz to 3800 MHz, of NR, B42, having a frequency rangefrom 3400 MHz to 4200 MHz, of Long Term Evolution (LTE), B43, having afrequency range from 3600 MHz to 3800 MHz, of LTE, B48, having afrequency range from 3550 MHz to 3700 MHz, of LTE, or B49, having afrequency range from 3550 MHz to 3700 MHz, of LTE.
 16. A communicationdevice, comprising: a radio frequency (RF) signal processing circuitthat is configured to process a radio frequency signal received by anantenna element; and the radio frequency circuit according to claim 1that is configured to transfer the radio frequency signal between theantenna element and the RF signal processing circuit.
 17. The radiofrequency circuit according to claim 1, wherein at least one end of thefirst acoustic wave filter or one end of the second acoustic wave filteris directly connected to the common terminal.
 18. The radio frequencycircuit according to claim 1, wherein at least one of the first acousticwave filter is directly connected to first LC filter or the secondacoustic wave filter is directly connected to the second LC filter. 19.The radio frequency circuit according to claim 1, wherein at least oneof the first LC filter comprises a terminal that is directly connectedto the first amplifier or the second LC filter comprises a terminal thatis directly connected to the second amplifier.